Understanding the physiology of the upper gastrointestinal (GI) tract is crucial to ensuring effective reflux management. Here you can learn all you need to know about the physiology of the stomach, oesophagus and acid secretion, as well as the pathophysiology and complications of reflux.

Upper GI anatomy and physiology

The stomach and the oesophagus are part of the upper GI tract. The lower oesophageal sphincter is a circular smooth muscle layer that lies at the gastroesophageal junction.

Mechanisms to prevent reflux

Lower oesophageal sphincterMaintains a pressure at the gastroesophageal junction greater than the intragastric pressure.

Crural diaphragmFunctions as an external sphincter, contributing towards the pressure at the gastroesophageal junction.

Flap valveExists where the oesophagus enters the stomach, acting as a physical barrier to the retrograde flow of stomach contents.

Once emptied of food, some residual acid remains in the stomach. During meals, this acid is neutralised by the food ingested, causing the production of new acid. This new acid sits on top of the ingested food and neutralised acid. This is known as the postprandial acid pocket and contributes to reflux.